The present invention relates to a blanking tool for making packaging blanks, and in particular relates to a moveable presser rail assembly for supporting blanking material during operation of the blanking tool.
It is well known in the manufacture of packaging containers, such as thin cardboard boxes for facial tissue, breakfast cereal, etc., that large packaging material sheets are cut to have a plurality of smaller sheets having identical outlines. The smaller sheets of material are referred to as blanks. One method of removing the blanks from the large sheets is to manually separate the blanks from the sheets, which is very labor intensive, and hence quite costly. An alternative method of removing the blanks from the large sheets is to use a male blanker on a top side of the large sheet that is cooperatively aligned with a female blanker on a bottom side of the sheet that supports the sheet.
As shown in FIG. 1, a male blanker 10 includes a plurality of presser members 12A, 12B, 12C, 12D, 12E secured to a support plate 13, and the presser members 12A-12E are dimensioned to be the same shape and slightly smaller than the blanks 14A, 14B, 14C, 14D, 14E of a large sheet 16 supported upon a female blanker 18. Next to and between the presser members 12A-12E are a plurality of prior art presser rails 20. (Only one of the identical six illustrated presser rails in FIG. 1 is identified by the reference number 20 to avoid confusion.) Each prior art presser rail includes two mount housings 22A, 22B that secure the presser rail 20 to the support plate 13. Each mount housing 22A, 22B includes a guide strut 24A, 24B that is secured within the mount housing by a spring biasing mechanism such as a captured coil spring (not shown), and the guide struts 24A, 24B are secured to the presser rail 20. The spring biasing mechanism forces the presser rail 20 in a direction away from the support plate 13 and mount housings 22A, 22B.
As is well known, in operation the support plate 13 is moved against the sheet 16 as shown in FIG. 2 so that the presser rail 20 secures the large sheet 16 as the presser members 12A-12E impact the blanks 14A-14E to force them to break apart from the large sheet 16 and move with gravity assistance and a stacking machine (not shown) to blank staking piles 26A, 26B, 26C, 26D, 26E. After the blanks 14A-14E are removed from the large sheet 16, the sheet is referred to as blanking scrap. As is apparent, the faster the large sheet 16 can be processed by the male and female blankers 10, 18, the more cost efficient is the blanking operation. A substantial limitation on efficient processing of the sheet 16 and blanks 14A-14E is associated with jamming of blanking scrap that is inadequately secured by the presser rails 20. The presser rails 10 must be able to apply a relatively uniform force to the large sheet 16, even when the sheet is not completely flat. Therefore it has become important that presser rail assemblies permit the presser rail 20 to evenly apply a force even when the rail 20 is not aligned to be parallel with a plane defined by the support plate 13, such as when a piece of blanking scrap is jammed between the presser rail and a subsequent large sheet.
Known presser assemblies have endeavored to solve this problem by permitting limited pivoting of a presser rail relative to a guide strut securing the presser rail to a support frame. For example, in U.S. Pat. No. 5,529,565 that issued on Jun. 25, 1996 to Oetlinger, which Patent is hereby incorporated herein by reference, a presser assembly is disclosed that has a presser rail having a first end pivotally mounted to a first guide strut, and a second end mounted either rigidly or pivotally to a second guide strut so that each end of the presser rail may move toward or away from a support plate independently of the other end of the presser rail. While the Oetlinger presser assembly does permit a uniform application of force to the presser rail by the guide struts while the presser rail is not parallel to the support plate, because at least one presser rail end is pivotally secured to the guide strut, the Oetlinger presser assembly is quite difficult to mechanically secure to the support plate, and requires a complicated and strong pivot joint between the guide strut and the presser rail. Therefore the Oetlinger presser assembly requires strong metal components that are costly to manufacture and assemble onto the support plate. Additionally, the Oetlinger presser assembly is typically manufactured with both rigid and pivoting guide rod components, so a user must stock, service and replace two different types of presser assemblies.
As is apparent from prior art FIGS. 1 and 2, as a different sized blank is to be made from a sheet 16, the presser rail 20 and mount housings 22A, 22B must be separated from each other and secured to differing positions on the support plate 13. Because the Oetlinger presser assembly includes a pivot mechanism between the guide rod and the presser rail, it is time consuming to disconnect the many pivoting guide rods and to re-connect them in new positions. Additionally, the presser rails must be manufactured to receive a pivot mechanism to enable pivoting between the presser rail and guide rod, rather than the presser rail having just a throughbore to be rigidly secured in a non-pivoting manner to the to the guide rod or strut.
Accordingly, there is a need for a simplified, pivoting or moveable presser rail assembly that affords inexpensive manufacture and installation of a presser rail to a support plate of a blanking tool.
The invention is a moveable presser rail assembly for supporting blanking material during operation of a blanking tool for making packaging blanks. The moveable presser rail assembly includes a mount housing having a cavity that defines at least one stop shoulder, a first conical shoulder and an opposed second conical shoulder that both protrude into the cavity. First and second tips of the first and second conical shoulders are at points of farthest protrusion of the shoulders into the cavity. A pivot sleeve is dimensioned to be secured within the cavity of the mount housing so that whenever an upper edge of the pivot sleeve contacts the stop shoulder, contact corners of first and second convex edges of the pivot sleeve are positioned adjacent to the tips of the first and second conical shoulders within the cavity of the mount housing. The first and second contact corners of the first and second convex edges of the pivot sleeve are defined as being a farthest distance from each other on the pivot sleeve. A guide strut is secured within the pivot sleeve by a spring biasing mechanism that biases a fastening end of the guide strut in a direction away from the mount housing. And, a presser rail is rigidly secured to the fastening end of the guide strut.
In use of the moveable presser rail assembly, the mount housing is secured over a throughbore of a support plate so that the fastening end of the guide strut passes through the throughbore to be rigidly secured to the presser rail, and the throughbore is dimensioned to have a substantially greater length than a diameter of the guide strut so that the guide strut may move in a direction that is not only perpendicular to a plane defined by the support plate. As the presser rail is moved directly toward the mount housing, the guide strut moves through the pivot sleeve within the cavity of the mount housing. Whenever the presser rail receives a force that is not perpendicular to the support plate but instead is toward and lateral to the support plate, the guide strut may move toward the support plate and laterally in such a non-perpendicular direction causing the contact corners of the convex edges of the pivot sleeve to slide out of contact with the tips of the conical shoulders. For example, if the presser rail were to move in a direction forcing the guide strut both toward the support plate and the second conical shoulder, the contact corner of the second convex edge of the pivot sleeve would slide up and over the second conical shoulder in a direction away from the support plate, while the opposed contact corner of the first convex edge of the pivot sleeve would slide down and away from the first conical shoulder in a direction toward the support plate. Whenever the lateral force is no longer applied to the guide strut through the presser rail, the spring biasing of the guide strut will return the contact corners of the convex edges of the pivot sleeve to be adjacent the tips of the conical shoulders so that the guide strut is returned to a normal or perpendicular position relative to the support plate and the presser rail is again parallel to a plane defined by the support plate.
By providing spring-biased, pivoting or lateral movement along with reciprocating movement of the guide strut relative to the support plate through the cooperative relationship of the pivot sleeve, stop shoulder and conical shoulders, the moveable presser assembly permits rigid attachment of the presser rail to the fastening end of the guide strut, rather than a complicated pivot assembly between the guide strut and presser rail. That rigid attachment greatly simplifies manufacture, assembly and replacement of the moveable presser rail assembly within a complicated work environment of a blanking tool.
In a preferred embodiment, the spring biasing means includes a forked spring receiver that is secured to the pivot sleeve and extends from the pivot sleeve in a direction opposed to the fastening end of the guide strut, and a spring end of the guide strut opposed to the fastening end includes a spring bore defined between opposed fingers of the guide strut. The spring receiver secures a first end of a coil spring and the opposed second end is secured within the spring bore of the guide strut. The guide strut may also include at least one mount shoulder that passes through a guide slot of the pivot sleeve toward the forked spring receiver in compressing the coil spring between the spring receiver and the guide strut, and when compressed, at least one lock rod may pass through the pivot sleeve dimensioned to restrict travel of the mount shoulder back through the pivot sleeve to thereby secure the spring biased guide strut within the pivot sleeve.
In such an embodiment, the pivot sleeve and spring biased guide strut are thereby prepared for insertion into the cavity of the mount housing through a cavity entrance. The mount housing may then be placed so that the cavity entrance overlies the throughbore of the support plate to which the moveable presser rail assembly is to be secured. The throughbore of the support plate is dimensioned to permit limited lateral movement of the guide strut, but is also dimensioned to have a width that is less than a longest distance between the contact edges of the pivot sleeve to restrict movement of the pivot sleeve out of the cavity of the mount housing. The presser rail may then be secured to the fastening end of the guide strut in preparing the blanking tool for operation.
By enabling lateral movement of the guide strut through the cooperative relationship of the pivot sleeve, stop shoulder, and conical shoulders, and thus enabling a rigid attachment of the guide strut to the presser rail, the moveable presser assembly provides for a strong assembly that may be fabricated of plastic materials that can he manufactured at modest cost compared to known high-strength, small-diameter metal components that provide for a presser rail to be pivotally mounted to a reciprocating guide cylinder. Additionally, because of the efficient and rugged design characteristics of the moveable presser rail assembly, a plurality of identical moveable presser rail assemblies may simply be secured to one presser rail, rather than known presser rail assemblies that require a first presser having a pivotable guide strut and a second presser having a rigid or slotted guide strut secured to a single presser rail to enable limited lateral, or non-perpendicular movement.
Accordingly, it is a general object of the present invention to provide a moveable presser rail assembly that overcomes deficiencies of prior art presser rail assemblies.
It is a more specific object to provide a moveable presser rail assembly that enables a presser rail to be rigidly secured in a non-pivoting manner to a guide strut of the assembly.
It is yet another object to provide a moveable presser rail assembly that provides for movement of a presser rail that moves in non-parallel alignment with a support plate supporting the assembly.
It is a further object to provide a moveable presser assembly that may be manufactured of plastic materials.
It is an additional object to provide a moveable presser rail assembly that facilitates assembly and replacement of a presser rail.
These and other objects and advantages of this invention will become more readily apparent when the following description is read in conjunction with the accompanying drawings.